Audio preamplifiers are important components in sound recording, reproduction, or audio for live concerts or events. In general, an audio preamplifier takes an electrical signal generated from a microphone or another sound source as an input, and further processes and amplifies this input signal to generate a desirable level of amplified electrical signal to other components such as main amplifiers, speakers, or recording equipment.
Preamplifiers take an important role in determining amplified and/or reproduced sound characteristics of the sound source, because it is generally the first actively-powered stage for the electrical signal generated from the microphone or another sound source, which are highly vulnerable to undesirable distortions or noise introduced during any amplification stages. For example, an undesirable introduction of distortions or noise at or before the preamplifier stage may be magnified by subsequent amplification stages, thereby making post-preamplifier stage correction difficult and exacerbating any problems from the preamplifier to recording equipment or a listener.
Various portable electronic devices in today's consumer electronics industry incorporate microphone-based audio recording capabilities. For example, a laptop computer, a smart phone, a video recorder, and other consumer electronic devices either integrate a microphone or connect to an external microphone to provide audio recording capabilities to consumers. Unfortunately, many consumer electronic devices today do not provide a professional-level hi-fidelity and linear recording characteristics for audio recording. Conventionally-integrated preamplifiers or amplifiers in consumer electronic devices often suffer from a poor signal-to-noise ratio and nonlinear recording characteristics. Unwanted distortions, noise, and/or nonlinear transformations of sound at an early amplification stage in the consumer electronic devices result in reduced recorded sound quality.
Therefore, it may be desirable to provide a novel pre-amplification gain circuit with a linear amplification and a high signal-to-noise ratio. Furthermore, it may be desirable to provide a novel pre-amplification gain circuit that is uniquely powered by a power source that also powers a microphone incorporated into or connected to a consumer electronic device. Moreover, it may also be desirable to provide a novel pre-amplification gain circuit that can be easily integrated into any consumer electronic devices that utilize an actively-powered microphone.